Mouse spinal and sensory neurons grown in dissociated cell culture have been studied with various biochemical and immunohistochemical methods. The research has focused on revealing the presence of specific membrane and cytoplasmic properties resident in cultured neurons. The principal observations from this year's research include: 1) the demonstration of glutamic acid decarboxylase activity in cultures of embryonic spinal neurons and its localization primarily to bouton-like structures investing cell bodies; 2) the demonstration of immunoreactivity to methionine- and leucine-enkephalin throughout the cytoplasm of 1-5 percent of spinal neurons; 3) the demonstration of immunoreactivity to dynorphin (1-13) at the level of the cell body in 1-5 percent of spinal neurons; 4) the demonstration by radioimmunoassay and immunohistochemistry of cholecystokinin and its receptors in sub-populations of cells; and 5) down-regulation of binding to benzodiazephines by chronic exposure to the drug.